Mount - ether42/bootable-usb GitHub Wiki
Using /dev/urandom as the key file means it will be recreated each time.
/etc/crypttab:
encrypted-lxc /dev/disk/by-id/ata-...-part2
encrypted-swap /dev/disk/by-id/ata-...-part3 /dev/urandom swap
/etc/fstab:
/dev/mapper/encrypted-swap none swap defaults 0 0